Squeeze the lemon. Chop cantuccini, chocolate and meringue separately. Stir mascarpone, liqueur, sugar, lemon juice, vanillin sugar and yoghurt until smooth. Wash the currants, dab dry and pluck from the stalks.
Set aside a few pieces of currants, meringue, chocolate and cantuccini for garnishing. Mix the remaining ingredients loosely just before serving and arrange in glasses. Decorate with chocolate, cantucchini, meringue and currants.